This invention pertains to a wire-feeding mechanism especially adapted to feed flux-cored welding wire, other malleable welding wires, etc. This invention makes no use of pinch rolls and similar devices as are typically employed in such mechanisms.
Prior wire-feeding mechanisms employing pinch rolls and similar devices are described in many patents including U.S. Pat. Nos. 3,093,285, 3,093,727, 3,107,291, and 3,395,308. Prior wire-feeding mechanisms without pinch rolls and similar devices are exemplified in U.S. Pat. Nos. 3,262,622, and 3,506,176.
When malleable wire is fed through pinch rolls and similar devices, particularly knurled rolls as commonly are employed for high traction, the wire is easily distorted into an out-of-circular cross-section, which cannot be accomodated by guide tubes and other components of an arc welding system. One possibility of such distortion is described as "finning" in U.S. Pat. No. 3,107,291.
When studied by electron microscopy, samples of welding wire as thus fed through knurled rolls have exhibited patterned discontinuities attributable to the knurling of the wire by the rolls. Such discontinuities are undesirable.